A-D convert apparatus, D-A convert apparatus and adjustment method

Abstract

An A/D conversion device including a first A/D conversion section and a second A/D conversion section that each include a D/A converter that has a plurality of bit capacitors corresponding to bits of input data, a comparing section that compares a reference voltage with a difference voltage obtained by subtracting an analog input voltage from an output voltage of the D/A converter, and a control section that detects a data value of the input data at which the difference voltage is substantially the same as the reference voltage and outputs the data value as digital data according to the input voltage, and an adjusting section that serially connects the bit capacitors of the D/A converter of the first A/D conversion section and the bit capacitors of the D/A converter of the second A/D conversion section that correspond to the same bits, and adjusts a capacity of at least one of the bit capacitors so that a voltage between the two bit capacitors approaches a middle point of voltages of the two bit capacitors.

1. An A/D conversion device comprising:
 a first A/D conversion section and a second A/D conversion section that each comprise: a D/A converter that has a plurality of bit capacitors corresponding to bits of input data; a comparing section that compares a reference voltage with a difference voltage obtained by subtracting an analog input voltage from an output voltage of the D/A converter; and a control section that detects a data value of the input data at which the difference voltage is substantially the same as the reference voltage and outputs the data value as digital data according to the input voltage; and 
 an adjusting section that serially connects the bit capacitors of the D/A converter of the first A/D conversion section and the bit capacitors of the D/A converter of the second A/D conversion section that correspond to the same bits, and adjusts a capacity of at least one of the bit capacitors so that a voltage between the two bit capacitors approaches a middle point of voltages of the two bit capacitors. 
 
     
     
       2. The A/D conversion device according to  claim 1 , further comprising a switch between output terminals that selects whether an output terminal to which the plurality of bit capacitors in the D/A converter of the first A/D conversion section are connected is connected to an output terminal to which the plurality of capacitors in the D/A converter of the second A/D conversion section are connected, wherein
 the adjusting section turns on the switch between output terminals and serially connects the bit capacitors of the D/A converter of the first A/D conversion section and the bit capacitors of the D/A converter of the second A/D conversion section that correspond to the same bits. 
 
     
     
       3. The A/D conversion device according to  claim 2 , wherein
 the D/A converter of the second A/D conversion section comprises: 
 a main D/A converter that has a plurality of bit capacitors corresponding to bits of input data; 
 a correction data output section that outputs correction data according to the input data; and 
 a sub D/A converter that has at least one correction capacitor corresponding to bits of the correction data outputted from the correction data output section, and 
 the adjusting section serially connects a bit capacitor of the D/A converter of the first A/D conversion section and a bit capacitor of the D/A converter of the second A/D conversion section corresponding to the same bit, a capacity of which is corrected by the correction capacitor according to the correction data, and adjusts the correction data so that a voltage between the two bit capacitors approaches a middle point of voltages of the two bit capacitors. 
 
     
     
       4. The A/D conversion device according to  claim 3 , wherein the adjusting section serially connects the bit capacitors of the D/A converter of the first A/D conversion section and the bit capacitors of the D/A converter of the second A/D conversion section and corrects the correction data on the basis of the comparison result between the reference voltage and a voltage between the two bit capacitors, which is outputted from the at least one comparing section of the first A/D conversion section and the second A/D conversion section. 
     
     
       5. The A/D conversion device according to  claim 3 , wherein the adjusting section serially connects the bit capacitors of the D/A converter of the first A/D conversion section and the bit capacitors of the D/A converter of the second A/D conversion section and corrects the correction data on the basis of the comparison result between the reference voltage and a voltage between the two bit capacitors, which is outputted from the comparing sections of the first A/D conversion section and the second A/D conversion section. 
     
     
       6. The A/D conversion device according to  claim 1 , wherein
 each of the D/A converters of the first A/D conversion section and the second A/D conversion section comprises: 
 a main D/A converter that has a plurality of bit capacitors corresponding to bits of input data; 
 a correction data output section that outputs correction data according to the input data; and 
 a sub D/A converter that has at least one correction capacitor corresponding to bits of the correction data outputted from the correction data output section, and 
 the adjusting section: modifies the correction data so that a voltage outputted from the D/A converter of the first A/D conversion section approaches a voltage according to the input data, in a first adjustment process for adjusting the D/A converter of the first A/D conversion section; and 
 serially connects a bit capacitor a capacity of which is corrected by the at least one correction capacitor of the first A/D conversion section and a bit capacitor corresponding to the same bit as that of the first A/D conversion section, a capacity of which is corrected by the at least one correction capacitor of the second A/D conversion section, and adjusts the correction data outputted from the correction data output section of the second A/D conversion section so that a voltage between the two bit capacitors approaches a middle point of voltages of the two bit capacitors, in a second adjustment process for adjusting the D/A converter of the second A/D conversion section. 
 
     
     
       7. The A/D conversion device according to  claim 6 , further comprising a third A/D conversion section that comprises: a D/A converter that has a plurality of bit capacitors corresponding to bits of the input data; a comparing section that compares, with the reference voltage, a difference voltage obtained by subtracting an analog input voltage from an output voltage of the D/A converter; and a control section that detects a data value of the input data at which the difference voltage is substantially the same as the reference voltage and outputs the data value as digital data according to the input voltage, wherein
 the adjusting section serially connects a bit capacitor a capacity of which is corrected by the at least one correction capacitor of the second A/D conversion section and a bit capacitor corresponding to the same bit as that of the second A/D conversion section, a capacity of which is corrected by the at least one correction capacitor of the third A/D conversion section, and adjusts the correction data outputted from the correction data output section of the third A/D conversion section so that a voltage between the two bit capacitors approaches a middle point of voltages of the two bit capacitors, in a third adjustment process for adjusting the D/A converter of the third A/D conversion section after the second adjustment process. 
 
     
     
       8. The A/D conversion device according to  claim 1 , wherein the first A/D conversion section and the second A/D conversion section interleave the input voltage, convert the interleaved voltage from analog to digital, and output the converted voltage as digital data. 
     
     
       9. An A/D conversion device comprising:
 a first A/D conversion section and a second A/D conversion section that each comprise: positive and negative D/A converters that have a plurality of bit capacitors corresponding to bits of input data; a comparing section that compares a voltage obtained by subtracting a positive input voltage from an output voltage of the positive D/A converter and a voltage obtained by subtracting an output voltage of the negative D/A converter from a negative input voltage; and a control section that detects a data value of the input data at which the output voltages outputted from the positive D/A converter and the negative D/A converter are substantially the same as each other and outputs the data value as digital data according to the input voltage; and 
 an adjusting section that serially connects the bit capacitors of the positive D/A converter of the first A/D conversion section and the bit capacitors of the negative D/A converter of the second A/D conversion section that correspond to the same bit, and adjusts a capacity of at least one of the bit capacitors so that a voltage between the two bit capacitors approaches a middle point of voltages of the two bit capacitors. 
 
     
     
       10. A D/A conversion device comprising:
 a first D/A converter and a second D/A converter that have a plurality of bit capacitors corresponding to bits of input data; and 
 an adjusting section that serially connects the bit capacitors of the first D/A converter and the bit capacitors of the second D/A converter that correspond to the same bits and adjusts a capacity of at least one of the bit capacitors so that a voltage between the two bit capacitors approaches a middle point of voltages of the two bit capacitors. 
 
     
     
       11. An adjusting method for an A/D conversion device comprising a first A/D conversion section and a second A/D conversion section that each comprise: a D/A converter that has a plurality of bit capacitors corresponding to bits of input data; a comparing section that compares a reference voltage with a difference voltage obtained by subtracting an analog input voltage from an output voltage of the D/A converter; and a control section that detects a data value of the input data at which the difference voltage is substantially the same as the reference voltage and outputs the data value as digital data according to the input voltage,
 the method comprising serially connecting the bit capacitors of the D/A converter of the first A/D conversion section and the bit capacitors of the D/A converter of the second A/D conversion section that correspond to the same bits, and adjusting an electric capacity of at least one of the bit capacitors so that a voltage between the two bit capacitors approaches a middle point of voltages of the two bit capacitors.